A search for Lambda Bootis stars in two OB associations, Orion OB1 and Lacerta OB1, has been carried out. One Lambda Bootis star has been discovered in the Orion OB1 association. In addition, nine A-type stars which appear to be slightly metal weak have been found in the two associations. The Lambda Bootis star is situated on the Zero-Age Main Sequence (ZAMS). The discovery of these stars strengthens the hypothesis that the Lambda Bootis stars are related to a short-lived evolutionary phase associated with the arrival of the star on the ZAMS.