Vishnu is not known as Pashupati directly by name but the title can be used as an ephithet for Vishnu. He controlled the pashus created by Prajapati with his strides where all the other devatas failed as per vedas
Pañcaviṃśa Brāhmaṇa 20.3.2
- प्रजापतिः पशूनसृजत तेऽस्मात् सृष्टा अपाक्रामंस्तानग्निष्टोमेन नाप्नोत् तानुक्थैर्नाप्नोत् तान् षोडशिना नाप्नोत् तान् रात्र्या नाप्नोत् तान् सन्धिना नाप्नोत् तानाश्विनेन नाप्नोत् ।
- तानग्निमब्रवीदिमान्म ईप्सेति ।
- तानग्निस्त्रिवृता स्तोमेन जराबोधीयेन साम्ना नाप्नोत् ।
- तानिन्द्रमब्रवीदिमान्म ईप्सेति ।
- तानिन्द्रः पञ्चदशेन स्तोमेन सत्त्रासाहीयेन साम्ना नाप्नोत् ।
- तान् विश्वान् देवानब्रवीदिमान्म ईप्सतेति ।
- तान् विश्वे देवाः सप्तदशेन स्तोमेन मार्गीयवेण साम्ना नाप्नुवन् ।
- तान् विष्णुमब्रवीदिमान्म ईप्सेति ।
- तान् विष्णुरेकविंशेन स्तोमेनाप्नोद्वारवन्तीयेनावारयतेदं विष्णुर्विचक्रम इति व्यक्रमत् ॥
- “Prajāpati created the animals (paśus). Having been created by him, they went away from him.
- He could not reach them by the Agniṣṭoma, nor by the Ukthas, nor by the Ṣoḍaśin, nor by the Night-rite, nor by the Saṃdhi, nor by the Āśvina.
- He said to Agni: ‘I desire to obtain these.’
- Agni could not reach them by the Trivṛt-stoma and the Jarābodhīya Sāman.
- He said to Indra: ‘I desire to obtain these.’
- Indra could not reach them by the Pañcadaśa-stoma and Satrāsāhīya Sāman.
- All the other gods failed to reach them
- He said to the Viśve Devāḥ: ‘I desire to obtain these.’
- The Viśve Devāḥ could not reach them by the Saptadaśa-stoma and Mārgīyava Sāman.
- He said to Viṣṇu: ‘I desire to obtain these.’
- Viṣṇu reached them by the Ekaviṃśa-stoma; by the Vāravantīya Sāman he restrained them (avārayat). Saying, ‘Here Viṣṇu strode,’ he strode.””
They are other references in Brahmana layers of vedas where Vishnu conquered the worlds for devatas and drove away asuras .