The 25-year-old Dutchman topped the time sheets in the morning at Sakhir, although the teams focused mostly on aerodynamic testing.
Verstappen won 15 of the 22 grands prix last year and will seek his third successive title when the 23-race season begins on March 5.
Ferrari’s Carlos Sainz was second, 0.294 seconds behind, despite leading much of the session, with Williams’ Alexander Albon third and the most laps (74).
“It’s always like the first day back at school, when everyone wears the new uniforms and sees the cars in their colours,” Red Bull boss Christian Horner said of the first day with all the 2023 cars together. on track.
Mercedes boss Toto Wolff said there was an air of excitement about getting back to racing and it was a productive first morning for a team, which had car problems last year.