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Livermore
Livermore
ZHEN

Westfield Capital Management Co LP

SEC CIK
0001177719
Latest filing
Aug 12, 2026

The latest 13F from Westfield Capital Management Co LP covers Q2 2026 (filed Aug 12, 2026): 278 long positions worth $30.6B. The top 10 holdings make up 29.2% of the portfolio, and the largest is NVIDIA Corp (NVDA) at 5.3%. Livermore has 22 filings on Form 13F from this institution, going back to Q1 2021.

What changed in Q2 2026

Share counts compared with Q1 2026: how many positions were new, added to, reduced or sold out, and the biggest buys and sells. Dollar amounts are estimated at the quarter-end prices implied by the filing.

Full comparison
New
68
Est. +$3.00B
Added
98
Est. +$5.03B
Reduced
104
Est. −$5.25B
Sold out
40
Est. −$1.29B

Top 5 holdings

Share of this quarter's portfolio value

  1. NVDANVIDIA Corp
    5.3%$1.62BHistory
  2. GOOGLAlphabet Inc.
    4.4%$1.34BHistory
  3. ASNDAscendis Pharma A/S
    4.2%$1.28BHistory
  4. AXONAxon Enterprise, Inc.
    2.7%$836.1MHistory
  5. FTAIFTAI Aviation Ltd.
    2.6%$794.6MHistory

Share of portfolio

Top 5 holdings and the other 273 positions, by share of portfolio value

  1. NVDA5.3%
  2. GOOGL4.4%
  3. ASND4.2%
  4. AXON2.7%
  5. FTAI2.6%
  6. Other 273 positions80.8%

Biggest buys

New and added positions, by estimated amount bought

  1. GOOGLAlphabet Inc.
    +$615.5MAddedHistory
  2. NVDANVIDIA Corp
    +$352.7MAddedHistory
  3. SNOWSnowflake Inc.
    +$259.0MAddedHistory
  4. AXONAxon Enterprise, Inc.
    +$239.6MAddedHistory
  5. AMDAdvanced Micro Devices Inc
    +$231.2MAddedHistory

Largest weight increases

New and added positions, by percentage points of the portfolio gained

  1. GOOGLAlphabet Inc.
    +1.93 pp2.4% → 4.4%History
  2. SNOWSnowflake Inc.
    +0.99 pp0.5% → 1.4%History
  3. AXONAxon Enterprise, Inc.
    +0.84 pp1.9% → 2.7%History
  4. AMDAdvanced Micro Devices Inc
    +0.76 pp<0.1% → 0.8%History
  5. MUMicron Technology Inc
    +0.72 pp0.1% → 0.9%History

Biggest sells

Reduced and sold-out positions, by estimated amount sold

  1. FIXComfort Systems USA Inc
    −$526.2MReducedHistory
  2. MRVLMarvell Technology, Inc.
    −$494.5MReducedHistory
  3. BEBloom Energy Corp
    −$357.5MReducedHistory
  4. AMZNAmazon Com Inc
    −$338.4MReducedHistory
  5. ALABAstera Labs, Inc.
    −$295.0MReducedHistory

Largest weight decreases

Reduced and sold-out positions, by percentage points of the portfolio lost

  1. AMZNAmazon Com Inc
    −1.32 pp2.0% → 0.7%History
  2. FIXComfort Systems USA Inc
    −1.29 pp3.6% → 2.3%History
  3. AAPLApple Inc.
    −0.90 pp3.3% → 2.4%History
  4. VRTVertiv Holdings Co
    −0.87 pp2.0% → 1.2%History
  5. MSFTMicrosoft Corp
    −0.84 pp2.6% → 1.7%History

Metrics

13F metrics for Q2 2026, computed only from the numbers in the filings. Definitions below.

Portfolio value
$30.6B
+$6.78B (+28.4%) vs. prior quarter
Positions
278
+28 vs. prior quarter
Top 10 concentration
29.2%
Top 10 as share of value
Turnover
24.0%
Q2 2026, one quarter
Average holding period
9.8 quarters
Weighted by value

How these are calculated

  • Portfolio value: the market value of all long positions in the 13F, as reported at quarter end, excluding options.
  • Top 10 concentration: the combined value of the 10 largest positions as a share of portfolio value.
  • Turnover: the smaller of this quarter's estimated purchases and estimated sales, divided by the average of this and last quarter's portfolio value. Estimates multiply the change in shares by the quarter-end price implied by the filing (market value divided by shares); new positions use this quarter's value and sold-out positions last quarter's. Only positions reported in shares count, and it is not calculated when the previous quarter was not filed.
  • Average holding period: how many consecutive quarters each current position has been held (including this one; a quarter without the position or without a filing starts the count over), weighted by this quarter's value. Counting starts with the first 13F in Livermore (Q1 2021), so positions held before then are understated.

13F filings by quarter

22 quarters, going back to Q1 2021. Bars show each quarter's 13F portfolio value; quarters without a filing are left blank.

Peak $30.6B (Q2 2026)

Q1 2021: $16.1BQ2 2021: $16.7BQ3 2021: $16.6BQ4 2021: $16.8BQ1 2022: $15.6BQ2 2022: $12.7BQ3 2022: $12.6BQ4 2022: $13.0BQ1 2023: $14.2BQ2 2023: $15.7BQ3 2023: $14.7BQ4 2023: $17.2BQ1 2024: $19.0BQ2 2024: $20.4BQ3 2024: $22.1BQ4 2024: $23.0BQ1 2025: $20.5BQ2 2025: $23.8BQ3 2025: $23.8BQ4 2025: $24.0BQ1 2026: $23.8BQ2 2026: $30.6B
Q1 2021Q2 2026
13F filings of Westfield Capital Management Co LP by quarter
QuarterFiledPositionsValueTop 3 holdingsChangesFiling
Q2 2026Aug 12, 2026278$30.6BNVDAGOOGLASNDvs. Q1 2026SEC
Q1 2026May 11, 2026250$23.8BNVDAASNDFIXvs. Q4 2025SEC
Q4 2025Feb 11, 2026241$24.0BNVDAASNDAAPLvs. Q3 2025SEC
Q3 2025Nov 12, 2025235$23.8BNVDAASNDMSFTvs. Q2 2025SEC
Q2 2025Aug 12, 2025239$23.8BNVDAASNDMSFTvs. Q1 2025SEC
Q1 2025May 9, 2025244$20.5BASNDNVDAAAPLvs. Q4 2024SEC
Q4 2024Feb 11, 2025239$23.0BNVDAAAPLMSFTvs. Q3 2024SEC
Q3 2024Nov 12, 2024247$22.1BNVDAAAPLMSFTvs. Q2 2024SEC
Q2 2024Aug 14, 2024248$20.4BNVDAMSFTAAPLvs. Q1 2024SEC
Q1 2024May 10, 2024244$19.0BMSFTASNDAAPLvs. Q4 2023SEC
Q4 2023Feb 9, 2024239$17.2BMSFTASNDAAPLvs. Q3 2023SEC
Q3 2023Nov 13, 2023234$14.7BAAPLGOOGLMSFTvs. Q2 2023SEC
Q2 2023Aug 11, 2023227$15.7BAAPLMSFTGOOGLvs. Q1 2023SEC
Q1 2023May 12, 2023222$14.2BAAPLMSFTASNDvs. Q4 2022SEC
Q4 2022Feb 13, 2023226$13.0BAAPLASNDMSFTvs. Q3 2022SEC
Q3 2022Nov 14, 2022230$12.6BAAPLMSFTGOOGLvs. Q2 2022SEC
Q2 2022Aug 12, 2022235$12.7BAAPLGOOGLMSFTvs. Q1 2022SEC
Q1 2022May 16, 2022235$15.6BAAPLGOOGLMSFTvs. Q4 2021SEC
Q4 2021Feb 10, 2022244$16.8BAAPLMSFTGOOGLvs. Q3 2021SEC
Q3 2021Nov 12, 2021235$16.6BAAPLGOOGLMSFTvs. Q2 2021SEC
Q2 2021Aug 10, 2021241$16.7BAAPLAMZNGOOGLvs. Q1 2021SEC
Q1 2021May 14, 2021243$16.1BAAPLAMZNGOOGL–SEC

13D and 13G filings

Companies where Westfield Capital Management Co LP reports owning 5% or more on Schedule 13D or 13G, and its latest filings.

Current stakes of 5% or more

1 company, largest stake first.

Companies where Westfield Capital Management Co LP owns 5% or more
CompanyLatest formStakeChangeFirst filedLatest filingFiling
ASNDAscendis Pharma A/S13G/A8.48%5.19M shares−0.70 ppfrom 9.18%Feb 2, 20235 filingsFeb 11, 2026SEC

Latest filings

28 filings on file made by Westfield Capital Management Co LP or listing it as a reporting person; the latest 20 are shown.

Schedule 13D and 13G filings by Westfield Capital Management Co LP
CompanyFiled (ET)FormStakeChangeEvent dateFiling
IMAXImax CorpJun 3, 202611:29 AM ET13G/A4.99%2.74M shares−0.02 ppfrom 5.01%Below 5%May 31, 2026SEC
IMAXImax CorpMay 5, 20264:18 PM ET13G5.01%2.70M sharesNewApr 30, 2026SEC
BCYCBicycle Therapeutics PLCMar 4, 202612:45 PM ET13G/A0.00%0.00 ppfrom 0.00%Below 5%Feb 28, 2026SEC
BCYCBicycle Therapeutics PLCMar 3, 20265:27 PM ET13G/A0.00%0 shares0.00 ppfrom 0.00%Below 5%Dec 31, 2025SEC
BCYCBicycle Therapeutics PLCMar 3, 20265:25 PM ET13G/A0.00%0 shares−6.04 ppfrom 6.04%Below 5%Dec 31, 2025SEC
BCYCBicycle Therapeutics PLCFeb 11, 202610:57 AM ET13G/A6.04%3.02M shares+0.55 ppfrom 5.49%Dec 31, 2025SEC
ASNDAscendis Pharma A/SFeb 11, 202610:57 AM ET13G/A8.48%5.19M shares−0.70 ppfrom 9.18%Dec 31, 2025SEC
FLYWFlywire CorpMar 5, 20252:16 PM ET13G/A0.00%0 shares−5.32 ppfrom 5.32%Below 5%Feb 28, 2025SEC
ASNDAscendis Pharma A/SFeb 11, 20259:15 AM ET13G/A9.18%5.53M shares0.00 ppfrom 9.18%Dec 31, 2024SEC
INVAInnoviva, Inc.Feb 11, 20259:12 AM ET13G/A0.00%0 shares–Below 5%Dec 31, 2024SEC
FLYWFlywire CorpFeb 11, 20259:11 AM ET13G5.32%6.52M sharesNewDec 31, 2024SEC
BCYCBicycle Therapeutics PLCFeb 11, 20259:09 AM ET13G5.49%2.61M sharesNewDec 31, 2024SEC
ASNDAscendis Pharma A/SFeb 10, 20255:13 PM ET13G/A9.18%4.08M shares–Dec 31, 2024SEC
MURAMural Oncology plcAug 5, 202413G/AOld format–––SEC
MURAMural Oncology plcJul 8, 202413G/AOld format–––SEC
MURAMural Oncology plcMay 8, 202413G/AOld format–––SEC
MURAMural Oncology plcApr 4, 202413G/AOld format–––SEC
ASNDAscendis Pharma A/SFeb 2, 202413G/AOld format–––SEC
MURAMural Oncology plcJan 10, 202413GOld format–New–SEC
IRWDIronwood Pharmaceuticals IncJul 5, 202313G/AOld format–––SEC