Here are the root position dominant seventh chords in the following major keys:
Key of C major - G7 (G dominant seventh)
Key of F major - C7 (C dominant seventh)
Key of B-flat major - F7 (F dominant seventh)
Key of E-flat major - Bb7 (B-flat dominant seventh)
Key of A-flat major - Eb7 (E-flat dominant seventh)
Key of D-flat major - Ab7 (A-flat dominant seventh)
Key of G-flat major - Db7 (D-flat dominant seventh)
Key of C-flat major - Gb7 (G-flat dominant seventh)